1. Field of the Invention
The present invention relates to a cock for controlling the flow rate of a fluid, particularly a pressurized gas, equipped with a lever pivoting about a pivot axis between at least three stable and angularly offset positions, namely a rest position, a liberating intermediate position and an active position, and to a gas container, such as a pressurized gas cylinder, equipped with such a cock.
2. Related Art
Industrial and medical gases are usually packaged in containers such as gas cylinders in which the gas is kept under a pressure that may be as high as 200 to 300 bar, or even more.
When there is a desire to use some pressurized gas, it is necessary to extract it from the container in which it was packaged, and to do this, use is made of a device known as a cock that allows the outlet and flow rate of fluid from the container to be controlled.
There also exist cocks that incorporate a pressure-reducing part so that the pressure of the fluid leaving the container can be reduced. These are then known as integrated pressure reducing cock assemblies, such an assembly being described in documents EP-A-747796 or EP-A-275242.
Many known cocks for gas cylinders have a common and very simple architecture, namely they are made up of a cock body, generally made of metal or metal alloy, such as brass, particularly comprising: a threaded base so that it can be fixed onto the neck of a gas cylinder for example; a gas outlet coupling via which the gas can be removed to the site where it is to be used; an internal passage formed in the cock body, fluidically connecting a gas inlet orifice borne by the base and via which the gas leaving the cylinder enters the cock body, and a gas outlet orifice borne by the outlet coupling and via which the gas which is passed through the cock body reemerges from said cock body and is then removed, via a gas line, for example, to its place of use; a system for controlling the flow rate to control the flow rate of gas in the internal passage formed in the cock body; and a manipulating means that can be actuated by an operator and collaborates with the flow rate control system to allow or prevent, as the operator desires, gas from being channeled through the internal passage and therefore from leaving via the outlet coupling.
The assembly comprising the inlet orifice, the internal passage and the outlet orifice is sometimes known as the gas distribution circuit.
Most of the time, the cock body also comprises a gas filling coupling with a fill orifice communicating fluidically, via a filling duct also formed in the cock body, with the internal gas passage so that the cylinder can be filled without having to remove the cock.
The assembly comprising the fill orifice and the filling duct connected to the internal passage is sometimes known as the gas filling circuit.
In most cases, the manipulating means with which existing gas cocks are fitted is or comprises a rotary hand wheel that can be operated by hand by the operator by turning it about its longitudinal axis, that is to say that a screwing-in operation performed by the operator on the hand wheel will partially or completely interrupt the flow rate of gas in the internal passage of the body by shutting off this internal passage via the flow rate control system, whereas a screwing out operation performed on the hand wheel will allow a partial or total flow rate of gas along the internal gas passage.
Such operating hand wheels are described in particular in the following documents: U.S. Pat. No. 4,103,806, EP-A-629812, WO-A-82/01580.
Furthermore, certain cocks or assemblies comprising cocks with inbuilt expansion valves comprise a manipulating means consisting of a lever pivoting about a pivot axis comprising a manipulating end allowing the lever to be grasped manually by the operator so that it can be pivoted angularly, and an active end, bearing the pivot axis, collaborating directly or indirectly with the system for controlling the flow rate of the gas so as to allow or, conversely, prevent, gas from being conveyed along the internal gas passage between the inlet orifice and the outlet orifice borne by the outlet coupling.
Such devices with manipulating levers are described in particular in the following documents: EP-A-747796, EP-A-990825, FR-A-2801689, EP-A-1026438 and GB-A-723828.
The use of a pivoting lever rather than of a rotary hand wheel has the particular advantage that it is quicker for the user to manipulate.
In addition, the position of the lever immediately reflects the status of the cock, that is to say the lever in the rest position corresponds to the passage of gas being interrupted, whereas the lever in the active position corresponds to the passage of gas. This avoids or minimizes the risk that the operator will make a mistake by increasing the safety of use.
The object of the present invention is to improve cocks of the lever-operated type.
Specifically, in existing lever-operated cocks, the lever usually pivots between two angularly offset stable positions, namely:                a first position known as the “rest position” in which the conveying of gas through the distribution circuit of the cock body is completely interrupted; and        a second position known as the “active position” or “gas release position” in which the conveying of gas through the distribution circuit of the cock body is allowed, that is to say is no longer interrupted.        
The switch from the rest position to the active position is accomplished by the operator pivoting the lever from its first angular position corresponding to the rest position of the lever into the second angular position corresponding to the active position.
Actuation of the lever gives rise to direct or indirect collaboration of the lever via its active end, with the gas flow rate control system in order to allow gas to pass through the passage opening which was hitherto shut off by the gas flow rate control system.
Furthermore, the switch from the active position to the rest position is accomplished by the operator operating the lever the other way.
This is clearly explained in document EP-A-747796 which discloses a pressure reducing cock with a pivoting lever pivoting between two extreme positions, open or closed, in which positions the lever is held stably and in a way that is practically insensitive to vibration.
Now, it has been found that, in order to better hold the lever in the rest position so as to ensure an effective shutting-off of the gas flow, it was desirable to hold the lever secured to the cock body by appropriate fixing means so as to avoid unwanted opening of the gas passage by unintentional actuation of the lever.
From there, a proposal was made to give the lever a catching mechanism allowing it to be secured to the cock body, thus guaranteeing a zero gas flow rate in the internal gas passage when the lever is held in its rest position.
However, in practice, it was found that with such a catching mechanism, problems could arise when moving from the rest position to the active position.
Specifically, if the catching mechanism holds the lever too firmly secured to the cock body then the operator may experience difficulty in detaching it when he wishes to pivot it and open the gas supply, and this may cause the operator to manipulate the lever excessively violently and cause excessively rapid opening of the gas flow, this being accompanied with the usual risks and problems that result from excessively sharp handling of pressurized gas. This disadvantage is accentuated all the more if the lever is attached to and held in the rest position very close to the cock body because then the space for the operator's hands or fingers may not be sufficient, especially if he is wearing working gloves.
Conversely, if the catching mechanism does not hold the lever sufficiently, then it will not play its part correctly.
The object of the invention is therefore to propose an improved lever-operated cock that allows the problem encountered when switching from the rest position to the active position to be solved, particularly when the lever is secured to the cock in its rest position by a catching mechanism.